Carbon dioxide has injurious effect on fresh concrete

(1)

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Carbon dioxide has injurious effect on fresh concrete

(2)

Ser

TH1

B92

~ N A L Y Z E D

CARBON

DIOXIDE

HAS

INJUFIJOUY

EFFEC,T

ON

FRESH CONCRETE

no.

28

c . ₂

Carbon

Sigxide

f r o m hznventad

salznanders or space

~ZG

_{h e a t e r s may}

_{b e hmmful}

t o

_{f r e s h}

_{c o ~ c r e t e ,}

_Difficulty

_{w i s e s}

during

w i n t e r cons

t r u c t l o n

in tf

ghtly

s e a l e d spaces where

temporary heating

equipment

is

used,

T h i s

is

t h e

c o n c l u s i o n

of

two e n g i n e e r s

of

the

Huron P o r t l a n d Cement Campany as

r e p o r t e d

in

t h e

J o u r n a l

of

t h e

F.meriean

C o n c r e t e I n s t i t u t e ,

December

1955,

The t w o e n g i n e e r s

were

c a l l e d

in

t o examine

a

c o n c r e t e

floor

I n

a

warehouse

in

N o r t h e r n

U n i t e d

S t a t e s ,

The

s u r f a c e

af

t h f

s

f l o o r , w h i c h was p l a c e d during t h e

w i n t e r ,

f a f l e d

to

horden,

Temporary

o i l

b u r n e r s

with

_{S l o w e r s}

_producing

_about

20OpQ00

B t u

e a c h

had

been used

to

keep

the

t e m p e r a t u r e

in

the

warehouse at

5 0 ' ~ .

b e f o r e , during, and

a f t e ~

p l a c i n e

t h e

con-

crete,

All

t h e

gases

f r o m the

b u r n e r s

were

r e l e a s e d i n t o

t h e

c

_lased-in

_{a r e a ,}

m e concrete

from

the floor

w a s malysed

a n d t h e r e

was

much

more s u r r a c e

c a r b o n a t i o n

than

would be expected

u n d e r

normal e x p o s u r e

c o n d i t i o n s ,

F ' u r t h e r

t e s t s

then

showed

t h a t

what

happened

to

the

f r e s h

c o n c r e t e

in

t h e

warehouse

due

t o

excessive

c a r b o n

d i o x i d e

i n

the

a f r

c o u l d be duplicated

in the

l a b o r a t o r y , .

Chemical.

h a r d e n e r s were

f o u n d

t o

b e

ineffective;

t h e

only

remedy was

round to

b e a

c o s t l y g r i n d i n g

o p e r a t i o n ,

Work is c o n t i n u i n g

t o

d e t e r d n e

t h e

e f f e c t

of

c a r b o n dioxlde

on

c o n c r e t e

u n d e r

v a ~ i o u s

exposure

c o n d i t t o n s and

w i t h

v a r i o u s

cements

and

e d m i x t u r e a .

The

r i s k

of

harmful

c o n c e n t r a t i o n s of

C 0 2

_will

o c c u r

where

unvented

b e a t e r s

ere

used

in

spaces

t h a t

ape tightly

s e a l e d

s o

_{t h a t}

_{v e n t i l a t t - i o n 1s}

_poor,

_In

_{t i g h t l y}

_{s e a l e d}

_{s p a c e s}

b e a t e r s

w h i c h

vent

t h e i r exhaust

gases

t o

the

o u t s i d e

S h o u l d

be used.

Where

t h i s

is n o t

tsassible,

the

c o n c r e t e

s h o u l d

b e

covered

as

s o o n a s

possible

with

a

membrane

c u r i n g

compound

or

v e n t i l a t i o n

should b e

provided

by

l e a v i n g

openings

l a o s e i y

s e a l e d

to

perrnlt a i r

leakage

i n t o

t h e

building,

Fro-

c a u t i o n s

need

only

be

t a k e n d u r t n p t h e

t w e n t y - f o u r

h o u r s

e t e r

p l a c i n g

t h e c o n c r e t e ,

December

1956

_(C.R.C.

₎

:

t

>

k,l

;-

* ?:

DlVlSlON OF BUILDING R E S E A R C H 0 NATIONAL RESEARCH COUNCIL m OTTAWA, C A N A D A